/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Base class for decorating ClassLoaders such as {@link OverridingClassLoader}
 * and {@link org.springframework.instrument.classloading.ShadowingClassLoader},
 * providing common handling of excluded packages and classes.
 *
 * @author Juergen Hoeller
 * @author Rod Johnson
 * @since 2.5.2
 */
public abstract class DecoratingClassLoader extends ClassLoader
{

    static
    {
        ClassLoader.registerAsParallelCapable();
    }


    private final Set<String> excludedPackages = Collections.newSetFromMap(new ConcurrentHashMap<>(8));

    private final Set<String> excludedClasses = Collections.newSetFromMap(new ConcurrentHashMap<>(8));


    /**
     * Create a new DecoratingClassLoader with no parent ClassLoader.
     */
    public DecoratingClassLoader()
    {
    }

    /**
     * Create a new DecoratingClassLoader using the given parent ClassLoader
     * for delegation.
     */
    public DecoratingClassLoader(@Nullable ClassLoader parent)
    {
        super(parent);
    }


    /**
     * Add a package name to exclude from decoration (e.g. overriding).
     * <p>Any class whose fully-qualified name starts with the name registered
     * here will be handled by the parent ClassLoader in the usual fashion.
     *
     * @param packageName the package name to exclude
     */
    public void excludePackage(String packageName)
    {
        Assert.notNull(packageName, "Package name must not be null");
        this.excludedPackages.add(packageName);
    }

    /**
     * Add a class name to exclude from decoration (e.g. overriding).
     * <p>Any class name registered here will be handled by the parent
     * ClassLoader in the usual fashion.
     *
     * @param className the class name to exclude
     */
    public void excludeClass(String className)
    {
        Assert.notNull(className, "Class name must not be null");
        this.excludedClasses.add(className);
    }

    /**
     * Determine whether the specified class is excluded from decoration
     * by this class loader.
     * <p>The default implementation checks against excluded packages and classes.
     *
     * @param className the class name to check
     * @return whether the specified class is eligible
     * @see #excludePackage
     * @see #excludeClass
     */
    protected boolean isExcluded(String className)
    {
        if (this.excludedClasses.contains(className))
        {
            return true;
        }
        for (String packageName : this.excludedPackages)
        {
            if (className.startsWith(packageName))
            {
                return true;
            }
        }
        return false;
    }

}
